Is mental illness considered insanity? Are the questioner and her family responsible for their harshness towards their brother who committed suicide, and what should they do?

Suicide is a grave major sin, based on the words of Allah Almighty: "And do not kill yourselves. Indeed, Allah is to you ever Merciful. And whoever does that in aggression and injustice – then We will drive him into a Fire. And that, for Allah, is [always] easy." If the person who committed suicide was mentally ill and unaware of their actions, then there is no sin upon them. If theality was intended as a disciplinary measure, we hope there is no sin upon you. We advise you to frequently supplicate for him, give charity on his behalf, and increase in supererogatory acts of worship and good deeds after the obligatory ones.